1. Technical Field
The present invention relates to nested tanks, and is particularly applicable to the construction of nested fuel and oxidizer tanks for a space vehicle.
2. Description of the Prior Art
It is known to provide a tank design for a space vehicle rocket stage in which the tanks are arranged coaxially. One design consists of a cylindrical body which is divided into two compartments by a common bulkhead. The forward compartment is usually the fuel tank for the rocket stage, and the rear compartment is usually the oxidizer tank for the rocket stage. The common bulkhead comprises a dome end of the forward compartment which is inverted so that it extends into the forward compartment. The common bulkhead also comprises a dome end for the rear compartment. The rear compartment dome end has a shape which geometrically matches the forward compartment dome end and is seated into but spaced from the forward compartment dome end.
In a space vehicle, the rear oxidizer compartment normally carries the higher pressure of the two compartments, and the dome end of the rear compartment is thus under tension loading. However, for safety and reliability reasons, the inverted dome end of the forward fuel compartment must be capable of carrying a negative or "compressive" pressure, in which the forward fuel compartment is at the higher pressure, without collapse or rupture. Accordingly, the two dome ends are structurally integrated by manufacturing them as a composite sandwich in which a honeycomb core is positioned between and bonded to the facing sides of the two dome ends. The honeycomb core sandwiched between the two dome ends provides the strength and stiffness necessary for the inverted common bulkhead to withstand a "compressive" pressure within the forward fuel compartment.
The common bulkhead must be absolutely leakproof since it frequently separates propellants which are hypergolic when mixed, and which may be at temperatures greater than a hundred degrees in difference. Thus, the manufacture of the common bulkhead to the reliability necessary for a space vehicle has heretofore required tight tolerance controls and labor intensive fitting, resulting in an expensive end product.
Prior U.S. Pat. No. 3,098,353 discloses a single cylindrical container having a partition which separates the container into a fuel tank and an oxidizer tank for a rocket engine. No details are disclosed concerning the structure of the partition.
Prior U.S. Pat. No. 3,190,305 also discloses a cylindrical container which has a partition defining aligned oxidizer and fuel tanks. This patent also contains no disclosure concerning details of the partition construction.
Pat. No. 3,426,529 discloses a cylindrical closed vessel having a transverse bulkhead dividing the vessel into a forward oxidizer section and an aft, fuel section. No details of the tank or bulkhead construction are disclosed.